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A8902CLBA Schematic ( PDF Datasheet ) - Allegro MicroSystems

Teilenummer A8902CLBA
Beschreibung 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING
Hersteller Allegro MicroSystems
Logo Allegro MicroSystems Logo 




Gesamt 12 Seiten
A8902CLBA Datasheet, Funktion
8902–A
3-PHASE BRUSHLESS DC MOTOR
CONTROLLER/DRIVER WITH BACK-EMF SENSING
LOAD
SUPPLY
1
V BB
COMMUTATION
DELAY
C D2 2
C WD 3
CST 4
24 C D1
23 DATA IN
22 CLOCK
21 CHIP SELECT
OUTA 5
GROUND 6
20 RESET
19 GROUND
GROUND 7
18 GROUND
OUTB 8
MUX
17 DATA OUT
OUTC 99
CENTERTAP 10
BRAKE 11
C RES 12
BOOST
CHARGE
PUMP
FLL 16 OSCILLATOR
VDD 15
LOGIC
SUPPLY
14 SECTOR
DATA
13 FILTER
Dwg. PP-040B
ABSOLUTE MAXIMUM RATINGS
at TA = +25°C
Load Supply Voltage, VBB . . . . . . . . . . 14 V
Output Current, IOUT . . . . . . . . . . . . ±1.25 A
Logic Supply Voltage, VDD . . . . . . . . . 6.0 V
Logic Input Voltage Range,
VIN . . . . . . . . . . . -0.3 V to VDD + 0.3 V
Package Power Dissipation, PD See Graph
Operating Temperature Range,
TA . . . . . . . . . . . . . . . . . . 0°C to +70°C
Junction Temperature, TJ . . . . . . . +150°C†
Storage Temperature Range,
TS . . . . . . . . . . . . . . . -55°C to +150°C
† Fault conditions that produce excessive junction
temperature will activate device thermal shutdown
circuitry. These conditions can be tolerated, but
should be avoided.
Output current rating may be restricted to a value
determined by system concerns and factors.
These include: system duty cycle and timing,
ambient temperature, and use of any heatsinking
and/or forced cooling. For reliable operation, the
specified maximum junction temperature should
not be exceeded.
The A8902CLBA is a three-phase brushless dc motor controller/
driver for use in 5 V or 12 V hard-disk drives. The three half-bridge
outputs are low on-resistance n-channel DMOS devices capable of
driving up to 1.25 A. The A8902CLBA provides complete, reliable,
self-contained back-EMF sensing motor startup and running algorithms.
A programmable digital frequency-locked loop speed control circuit
together with the linear current control circuitry provides precise motor
speed regulation.
A serial port allows the user to program various features and
modes of operation, such as the speed control parameters, startup
current limit, sleep mode, diagnostic modes, and others.
The A8902CLBA is fabricated in Allegro’s BCD (Bipolar CMOS
DMOS) process, an advanced mixed-signal technology that combines
bipolar, analog and digital CMOS, and DMOS power devices. The
A8902CLBA is provided in a 24-lead wide-body SOIC batwing package.
It provides for the smallest possible construction in surface-mount
applications.
FEATURES
s DMOS Outputs
s Low rDS(on)
s Startup Commutation Circuitry
s Back-EMF Commutation Circuitry
s Serial Port Interface
s Frequency-Locked Loop Speed Control
s Sector Data Tachometer Signal Input
s Programmable Start-Up Current
s Diagnostics Mode
s Sleep Mode
s Linear Current Control
s Internal Current Sensing
s Dynamic Braking Through Serial Port
s Power-Down Dynamic Braking
s System Diagnostics Data Out
s Data Out Ported in Real Time
s Internal Thermal Shutdown Circuitry
Always order by complete part number, e.g., A8902CLBA .






A8902CLBA Datasheet, Funktion
8902–A
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
FUNCTIONAL DESCRIPTION
Power Outputs. The power outputs of
the A8902CLBA are n-channel DMOS
transistors with a total source plus sink rDS(on)
of typically 1 . Internal charge pump boost
circuitry provides voltage above supply for
driving the high-side DMOS gates. Intrinsic
ground clamp and flyback diodes provide
protection when switching inductive loads and
may be used to rectify motor back-EMF in
power-down conditions. An external Schottky
power diode or pass FET is required in series
with the load supply to allow motor back-EMF
rectification in power down conditions.
Back-EMF Sensing Motor Startup and
Running Algorithm. The A8902CLBA
provides a complete self-contained back-EMF
sensing startup and running commutation
scheme. The three half-bridge outputs are
controlled by a state machine. There are six
possible combinations. In each state, one
output is high (sourcing current), one low
(sinking current), and one is OFF (high
impedance or Z). Motor back EMF is sensed
at the OFF output. The truth table for the
output drivers sequencing is:
Sequencer
State
1
2
3
4
5
6
OUTA
High
Z
Low
Low
Z
High
OUTB
Low
Low
Z
High
High
Z
OUTC
Z
High
High
Z
Low
Low
backward, or remain stationary (if in a null-torque position). If the motor
moves, the back-EMF detection circuit waits for the correct polarity
back-EMF zero crossing (output crossing through centertap). True
back-EMF zero crossings are used by the adaptive commutation delay
circuit to advance the state sequencer (commutate) at the proper time
to synchronously run the motor. Back-EMF zero crossings are indi-
cated by FCOM, an internal signal that toggles at every zero crossing.
FCOM is available at the DATA OUT terminal via the programmable
data out multiplexer.
V OUTA
V OUTB
V OUTC
SOURCE ON
V CTAP
BACK-EMF VOLTAGE
SINK ON
FCOM TOGGLES AT
BACK-EMF ZERO CROSSING
FCOM
Dwg. WP-016-1
Startup Oscillator. If the motor does not move at the initial startup
state, then it is in a null-torque position. In this case, the outputs are
commutated automatically by the startup oscillator after a period set by
the external capacitor at CST where
tCST =
4(VCSTH - VCSTL) x CST
IST(charge) + IST(discharge)
At startup, the outputs are enabled in one
of the sequencer states shown. The back
EMF is examined at the OFF output by
comparing the output voltage to the motor
centertap voltage at CENTERTAP. The
motor will then either step forward, step
In the next state, the motor will move, back EMF will be detected,
and the motor will accelerate synchronously. Once normal synchro-
nous back-EMF commutation occurs, the startup oscillator is defeated
by pulses of pulldown current at CST at each commutation, which
prevents CST from reaching its upper threshold and thus completing a
cycle and commutating.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

6 Page









A8902CLBA pdf, datenblatt
8902A
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
Allegro MicroSystems, Inc. reserves the right to make, from time to
time, such departures from the detail specifications as may be required
to permit improvements in the design of its products.
The information included herein is believed to be accurate and
reliable. However, Allegro MicroSystems, Inc. assumes no responsibil-
ity for its use; nor for any infringements of patents or other rights of third
parties which may result from its use.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

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